Arrangement for detecting and evaluating yawing movements

ABSTRACT

The present invention provides an arrangement for detecting and evaluating yawing movements of an automotive vehicle, serving as an input quantity of an automotive control system, comprising yaw rate sensors (GRS) and electronic circuits (SCU) for processing and evaluating the information obtained by the yaw rate sensors (GRS) and representing the yawing movement of the automotive vehicle, and for generating control signals. Moreover, one or more electronic compass systems (KB, KH) are provided that detect yawing movements of the vehicle independently of the information obtained by the yaw rate sensors (GRS). By comparing the information supplied by the compass systems (KB, KH) to the information supplied by the yaw rate sensors (GRS), the operation of the measuring systems or measuring channels (KB, KH, GRS) is monitored.

BACKGROUND OF THE INVENTION

The present invention is concerned with an arrangement for detecting andevaluating of yawing movements of an automotive vehicle which serve asan input quantity of an automatic control system, comprising one or moreyaw rate sensors and electronic circuits for processing and evaluatingthe information obtained by the yaw rate sensors and representing theyawing movements of the automotive vehicle, and for generating controlsignals.

Measuring and evaluating of yawing movements, namely of angular motionsand yawing speeds about the vertical axis of an automotive vehicle, areparticularly important in connection with automotive control systemswhich applies especially to the so-called driving stability control (FRSor ASMS, i.e. automatic stability management system).

Systems for automotive vehicles for controlling and limiting undesiredyawing movements about the vertical axis of a vehicle are already knownin the art. Intensive development work is designed to improve suchsystems and to cut manufacturing costs thereof.

In systems of the afore-described type, basically, steering angle, gaspedal position, brake pressure and motion pattern of the vehicle wheelsare detected with the aid of sensors, with the nominal yawing movementof the automatic vehicle being computed from such data. At the sametime, the transverse acceleration acting upon the automotive vehicle,and the yawing speed are measured. The actual state of yaw of theautomotive vehicle is determined from the arithmetic combination ofthese qualities. If a non-permissive deviation of the actual movementfrom the nominal movement is detected or imminent, the control isactivated, limiting the yawing movement by a controlled actuation of thebrake to permissive values not affecting the driving stability.

Driving stability control systems of the afore-described type arerequired to work with a high precision and reliability in order that thestandard and proper driving behavior of the automotive vehicle bemaintained, preventing an early activation of the control systemaffecting the driving comfort or even causing a danger or irritation tothe driver.

To that effect, a precise, reliable and error-free determination of therate of yaw is required. Error-free measured values of the rate of yawmust be detected before the control is affected. It is difficult tomeasure the yawing movement and to monitor the measuring systems becauseno defined vehicle motions can be generated in reference to which theyaw rate sensors and the associated evaluating circuits could be checkedor calibrated. It is only during standstill of the vehicle thatdeviations from the zero point can be rectified.

State-of-the-art driving stability control systems employ a singlerelatively high-precision yaw rate sensor. However, this conceptioninvolves the disadvantage that after calibration of the sensor, duringstandstill of the automotive vehicle, it is no longer possible todirectly identify a slowly progressing measured deviation. Such“creeping” inaccuracies can occur as a result of defects of specialsensor components or of the evaluating circuits, i.e. as a result ofdefective condensers, open, high-ohmic semi-conductor inputs, totteringcontacts etc.

Errors of this type can only be identified via circumferential factorsobtained from auxiliary data or through logical operation that are onlyindirectly related to the yawing movement. The identifying mechanismresponds by a relatively poor resolution and by a higher inertia ordelay than in direct reference processes.

To compensate these disadvantages, it will be necessary to detect, inpractice, correspondingly more accurate measured values, requiring, inturn, employment of high-precision yaw rate sensors able to provide botha large measuring range and a high dissolution and precision in thesmall-to-average yaw rates ranges. However, this involves anout-of-proportion relationship between technical efforts and achievableaccuracy.

Despite high efforts involved, detection of each and every malfunctionof the sensor cannot be safeguarded so that, for safety reasons, thecontrol system will have already to be cut off if temporarycircumstances occur arousing the suspicion of malfunction of the system.If such an error or suspected defect occurs during a control operation,the behavior of the system is indefinite. To reduce the malfunctionprobability to a reasonable degree, maximum requirements must be placedupon the reliability of the components and upon the automatic testfunction of the sensing system and of the appertaining circuits. Suchrequirements can, of course, only be complied with by accepting highmanufacturing efforts.

It is, therefore, the object of the invention to overcome theafore-described disadvantages involved with conventional systems andsensors and to provide an arrangement of the afore-described typeenabling accurate and safe detection of the yawing movement of anautomotive vehicle, keeping the efforts and expenses involved lowcompared to conventional systems, and insuring a quick and safe errordetection.

SUMMARY OF THE INVENTION

It has been found that this problem can be solved by providing one orseveral electronic compass systems able to detect yawing movements ofthe vehicle independently of the information obtained by the yaw ratesensors, and in that function and accuracy of the measuring systemsindependent of one another are monitored by comparing the informationsupplied by the compass system to the information supplied by the yawsensors.

According to a preferred form of embodiment of the invention, twocompass systems arranged in spaced relationship on the vehicle are usedin connection with the yaw rate sensors, with the information providedby the two compass systems being compared to the information supplied bythe yaw rate sensors for detecting the yawing movements. It isparticularly advantageous to arrange one of the two compass systems onthe front end and the other on the tail of the vehicle. Specialinformation can be obtained—as will be described hereinafter in greaterdetail—from the successive occurrence of the output signals of thecompass in conjunction with the vehicle movement and travel direction.

An essential feature of the arrangement of the invention resides in thatseveral measuring channels independent of one another exist on the basisof the yaw rate sensors and of the compass systems to supply outputsignals and information, respectively, enabling, by reference andlogical operation, the function of the individual measuring channels tobe reliably monitored and the different errors inclusive of so-called“creeping” errors to be detected in due time.

Further features, advantages and fields of application of the inventionare disclosed by the following description of details with reference tothe enclosed drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings,

FIG. 1 is a schematically shown perspective view of an automotivevehicle the vertical axis of which is the reference axis for the yawingmovement, and

FIG. 2 is a schematically shown view of the basic arrangement of themeasuring channels relative to the plane of travel of an automotivevehicle.

DETAILED DESCRIPTION OF THE DRAWINGS

FIG. 1 only serves to show the yawing movement of an automotive vehicle1 which is defined as a rotary movement about the vertical axis Z of thevehicle in the direction of arrow GR. Yawing movement, yawing speed,yawing acceleration and yawing moment have an impact on the drivingstability of an automotive vehicle and are, therefore, input qualitiesof vehicle control systems.

The present invention is based on a modified conception for sensing theyaw rate. The use of compass systems in conjunction with one or more yawrate sensors, and the employment of several measuring channelsindependent of one another, virtually, substantially simplifies andimproves sensing of the rate of yaw.

FIG. 2 schematically shows the structure of an automotive vehicle 1including an arrangement of the type provided by the invention. Arrow Rschematically indicates the direction of travel of the vehicle 1 asshown when driving straight forward. Reference characters VL, VR referto the front wheels; reference characters HL, HR to the rear wheels ofan automotive vehicle.

In the form of embodiment as shown, the arrangement of the inventioncomprises a yaw rate sensor GRS and two compass systems KB, KH of whichcompass system KB is arranged in the front end and compass system KH inthe tail of the vehicle.

The (processed) output signals of the yaw rate sensor GRS and of the twocompass systems are worked and evaluated in a processor, namely amicrocomputer or microcomputer system. Controllers or control systems ofthis type based on complex microcomputers or microcomputer systems arecommonly used in the modern vehicle control technology. FIG. 2 shows asignal processing step SCU which is understood to be a component of theelectronic unit of a driving stability control system.

An important feature of the arrangement of the invention resides in thesimultaneous use of a plurality of measuring channels independent of oneanother. In the example according to FIG. 2, these are the measuringchannels comprising the two compass systems KB and KH and the yaw ratesensor GRS. By combining the output signals or the data of the yaw ratesensors contained in the output signals with and comparing the same to acompass system KB or KH, the operation of the measuring channels will bemonitored. By arranging the compass systems — therefor KB or KH instaggered relationship in the direction of travel R—in the vehicle frontend (KH), on the one hand, and in the tail of the vehicle (KB), on theother—a misdirection of the compass under consideration of the directionof travel can be reliably detected.

The yaw rate of the vehicle is continuously computed from the outputsignals of the compass systems and is then compared to thetime-associated measured values of the yawing rate sensor GRS. By sousing a plurality of measuring channels on the basis of compass systemsand yawing rate sensors—depending on the type ofimplementation—different advantages and types of information areobtained. However, the basic advantages over the prior art measurementof the yawing movement with the aid of a single, complex yawing ratesensor are always identical. Firstly, the advantages reside in that theparallel operation of a plurality of measuring channels enables theindividual measuring channels and compass systems, respectively, andsensors with associated evaluation circuits to be mutually monitored.The degree of conformity of the yawing rate values synchronouslydetected or computed on the basis of the compass systems KB, KH and ofthe yaw rate sensor GRS can be used as a direct measurement of theoperating safety of the yaw rate sensing system.

When permanently monitoring the measuring channels, defective conditionsof structural components, including slowly developing or “creeping”defects of one of the sensors or compass systems involved, can bedirectly and safely identified. The vehicle control system can then becut off in time by a known per se monitoring circuit (not shown).

A modified form of embodiment resides in that in case of occurrence of atotal failure of the sensor during a control operation which failure is,of course, equally detected by using the parallel measuring channelsindependent of one another, the control system can alone be operated,for an emergency period, on the basis of the data and signals providedby the intact sensor or the intact compass system.

Accordingly, the arrangement of the invention, as a result of the use ofthe additional compass systems, involves substantial advantagesregarding operating safety, achieving. at the same time, ahigh-precision yaw rate measurement by using the yaw rate sensor; theseadvantages are achieved with relatively low technical and manufacturingefforts.

Due to the arrangement of the two compass systems KB, KH in staggeredrelationship in accordance with the embodiment of FIG. 2, alsoirregularities of the terrestrial magnetic field, to which a compassresponds, can be detected in that first the compass system KB and thenthe compass system KH are required to respond in the same way both whenentering and when leaving a trouble zone (e.g. a tunnel). Once thevehicle speed and, hence, of the phase shift between the output signalsof the systems KB and KH due to the vehicle speed are known, amisdirection of the compass can be reliably detected and analyzed toperform a corresponding calibration.

What is claimed is:
 1. An arrangement for detecting and evaluating ofyawing movements of an automotive vehicle as an input quantity of anautomotive vehicle control system, comprising: at least one yaw ratesensor and electronic circuits for processing data from the at least oneyaw rate sensor for generating control signals; and at least twoelectronic compass systems detecting yawing movements independently ofthe data obtained by the at least one yaw rate sensor the compasssystems being positioned remote from each other in the direction oftravel of the automotive vehicle.
 2. An arrangement according to claim1, including a unit for comparing the data supplied by the compasssystems with the data supplied by the at least one yaw rate sensor. 3.An arrangement according to claim 1, wherein one compass system islocated near the front end and another compass system is arranged nearthe tail of the automotive vehicle.
 4. An arrangement according to claim1, wherein flux gate-type compass systems are provided as compasssystems.
 5. An arrangement according to claim 1, wherein at least onesensor based on a tuning-fork oscillator of quartz is the at least oneyaw rate sensor.